This project concerns the analysis of single unit responses in the optic tract, lateral geniculate nucleus and visual cortex of cats and monkeys. Novel methods of nonlinear systems analysis will be used to dissect the responses of visual neurons into linear and nonlinear components. One of our basic projects will be synthesis of ganglion cell responses to arbitrary stimuli in order to illustrate the completeness of a theoretical model of the retina developed in our laboratory. The relation of the nonlinear subunits in the receptive fields of Y ganglion cells to the long-range periphery effects will be analyzed, using the nonlinear analysis techniques mentioned above. We will also study the spatial distribution of the contrast gain control in the retina. The role of the lateral geniculate nucleus will be defined by studying center-surround interactions and nonlinear, suppressive interactions in simultaneous recordings of LGN cells and their main retinal inputs. In the monkey geniculate, cells in different laminae will be analyzed as X or Y to examine the hypothesis that X and Y cells are segregated. Spatial resolution, linearity of spatial summation, and conduction velocity of retinal afferents will be studied in single cells of the visual cortex, in order to assess how much serial processing and parallel processing contribute to the receptive fields of cortical cells.